The height and width of containers used with self-propelled or towed transport equipment for hauling harvested whole stalk sugarcane from the field has increased over the years in an effort to minimize transportation costs due to increased fuel costs. The additional height, in turn, requires the sugar cane whole stalk loader to lift the cane higher in the air in order to clear the top of the transport container. The additional width of the transport container has caused problems with physical contact between the loader and the transport container, thereby necessitating that the loader and container operate further apart. As sugarcane is planted in raised beds or rows, it is necessary for the transport unit to move one additional row away from the loader even though the additional width of the transport container may only be one foot. In some areas of the world, this could be up to six feet. This, of course, necessitates a longer reach for the loader and leads to instability as the load has to be moved further from the center of gravity of the loader. Some manufacturers have solved the problem by building larger loaders that straddle two rows of cane for stability and have loading booms capable of both high and long reach. Further, the swivel mast of such larger loaders are normally supported only at their base and this requires a robust bearing structure. These solutions all result in higher manufacturing costs.
Side-mounted sugar cane loaders, whether tractor-mounted or dedicated loaders built only for that purpose, use the same swivel mast boom mechanism. A vertical pin is supported on the bottom side at a fixed mounting point on the machine. A pair of removable diagonal braces for supporting the swivel mast pin are arranged perpendicular to each other and have upper ends coupled to the top of the pin and lower ends attached to the machine. One of the diagonal braces is basically parallel to the direction of travel of the machine while the other diagonal brace is transverse or normal to the direction of travel. The brace parallel to the direction of travel carries the top pin load when the loader boom is lifting from the front of the machine. The transverse brace carries the top pin load when the swivel mast, which is in the form of a hollow tube received on the pin, is rotated about the pin so as to support the loader boom for working at the side. At positions in between those for front and side operation, the two diagonal braces share the load. The swivel mast has mounting points at its lower end for being coupled to one or two hydraulic cylinders that provide the force for rotating the mast. The swivel mast is also provided with a mounting point for pivotally attaching an inner end of a main or inner boom section, and another mounting point for one end of a hydraulic boom cylinder that has its other end coupled to the main boom section. Another hydraulic cylinder is coupled between the main boom section and an outer or sub-boom section, the latter having an articulated grab mechanism coupled to its outer end. The function of the grab mechanism is to encircle a bundle of cane stalks, and then close about the bundle in a constricting manner for preventing the cane stalks from falling back to the ground. Once the grab closes on the bundle of cane stalks, the two boom cylinders are activated such that the grab is lifted into the highest position. The swivel mast is then pivoted 90° to the direction of travel so as to position the loaded grab over the container of the transport unit traveling alongside the loader. The grab is then opened and the stalks of cane are deposited in the container. It is during the side rotate process that adequate clearance between the loader and transport must be provided.
Known cane loaders of the swivel mast design often have both the mounting point for the boom and for the hydraulic boom lift cylinder located at the front side of the mast that comes closest to the transport unit. U.S. Pat. No. 2,874,854 discloses a slightly different arrangement wherein the mounting points for the boom and the boom cylinder are located on the axis of the swivel mast. In one embodiment (see FIG. 1), no diagonal brace is provided for the swivel mast, while in a second embodiment (see FIGS. 5 and 6), a pair of diagonal braces 75 are provided. Without the top being supported, it would take a very large diameter pin and a robust bearing arrangement at the base of the pin, to carry the bending moment induced by the load of cane and the lift cylinder. Such an arrangement is similar to that of large cane loaders that have the boom and lift cylinder coupled to the top of a mast cantilevered off a large Rotek® type bearing.
In a typical cane loader, the tire centers are slightly outboard of the centers of the furrows between adjacent cane rows, and the swivel mast center is located just inboard of the tire centerline so as to be on the centerline of the furrow. The loaders are usually equipped with a push piler for gathering harvested cane that has been deposited in the furrow; and this piler includes cane-engaging tines that are spaced apart so as to define a pocket centered relative to the furrow centerline. This makes it possible then for the loader to be equipped with a non-rotating grab, since with the loader boom rotated to the front, the grab will be properly oriented for closing crosswise to the cane, which is oriented crosswise to the centerline of the furrow. For a more complete explanation of the theory of operation, see U.S. Pat. Nos. 4,614,476; 4,609,318; and 5,285,856.
In recent years, as the height and width of containers of sugarcane transporters have increased, some manufacturers have moved the center of the swivel towards the center of the tractor to gain clearance between the swivel mast boom components and the transport unit. With loaders equipped with a non-rotating grab, the cane-engaging tines, and hence, the pocket of the push piler are also moved closer to the row passing centrally beneath the tractor so that the bunched cane stalks will be better located for engagement by the grab of the loader. This results in the inside tine of the piler engaging the ground in the root zone of the cane stubble located in the row. Since sugarcane re-grows from the root system, any damage to the root system negatively impacts the yield the following year.
An additional drawback that has been observed relative to known loader boom arrangements associated with cane stalk loaders is that the relationship between the line of action of the boom lift cylinder or actuator and the point of pivotal connection of the inner boom section with the swivel mast is such that the lever arm between the line of action and the point of pivotal connection sharply decreases as the boom is lifted, which results in the speed at which the boom section is lifted increasing sharply during the lifting operation. This increasing speed is undesirable since there is considerable moment of inertia due to the loaded cane grab and the moving boom components that must be arrested prior to the lift actuator reaching the end of its stroke in order to avoid an unwanted shock load on the boom arrangement.
What is needed is an inexpensive way to gain clearance between the loader boom and the container of the transporter unit without negatively impacting the relationship of the piler pocket and the furrow center, and at the same time, to present a loader boom structure which is simpler to control in order to avoid shock loads during the raising and positioning of a loaded grab for depositing the cane in a container of a cane transport.